What is the lowest score you have achieved on EFF Cover Your Tracks?
On Librewolf i got 16.48 bits of information, on TOR browser 10.32 bits, but on Tails I managed to get only 9.3 bits.
https://coveryourtracks.eff.org/
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9.3 bits / 1:628.3 (ipadOS / safari)
...how do they quantify 3/10 of a bit?..
They probably give entropy value, average number of, yes or no, questions that are needed to identify You. (Guess all the information that your browser provided)